Multiscale atmospheric simulation using the spectral element method Aim Fournier NCAR also with F' B - PowerPoint PPT Presentation

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Multiscale atmospheric simulation using the spectral element method Aim Fournier NCAR also with F' B

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Identification and prediction of regional climate should help ... Aries DyCore. Other symbols for other models. Gflops. Parallel scaling on various computers ... – PowerPoint PPT presentation

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Title: Multiscale atmospheric simulation using the spectral element method Aim Fournier NCAR also with F' B


1
Multiscale atmospheric simulation using the
spectral element methodAimé Fournier
(NCAR)also withF. Baer, Houjun Wang (UMCP)A.
Pouquet, D. Rosenberg, J. Tribbia (NCAR)Mark
Taylor (Sandia)

2
Why Do This
  • Variable resolution in a model helps define
    climate
  • Nonlinear effects introduced by regional scales
    must be incorporated into a climate
  • Smaller scale effects often grow on shorter time
    scales
  • Identification and prediction of regional climate
    should help in understanding the evolution of the
    global climate.
  • Integrations must be sped up to perform all
    computations needed for solving the climate
    modeling problem.

3
SEACM Spectral Element Atmospheric Climate Model
What is the model?
  • A global model with an unstructured grid and some
    useful features
  • Uses geometric properties of finite element
    methods
  • Incorporates local mesh refinement and regional
    detail
  • Takes advantage of parallel processing
  • Maintains the accuracy of spectral models
  • Is computationally efficient
  • Has no pole problem.

4
Setting The Model Domain
  • Tile the spherical surface with arbitrary number
    and size of rectangular elements
  • Inscribe a polyhedron with rectangular faces
    inside sphere,
  • Map surface of polyhedron to surface of sphere
    with a gnomonic projection,
  • Use the cube (most elementary polyhedron),
  • Subdivide each of the six faces of the cube as
    desired.
  • Can use Local Mesh Refinement (LMR) as desired.

5
Subdivision 1
Cube
Uniform Resolution Rectangles
6
Quick Summary of the Integration Process
  • Represent the prediction equations in integral
    form
  • Use Gauss-Lobatto quadrature for integration
  • Use Legendre cardinal functions for the basis
    functions
  • Use test functions based on the Legendre cardinal
    functions.
  • These choices result in an extremely simple
    finite element method with a diagonal mass
    matrix.

7
Examples of Picture Framing
Basic grid
Expanded grid (3x3)
LMR on the globe
8
Topography w/o LMR
T42
T85
Note Each element has an 8x8 grid
Note Each element has an 8x8 grid
9
Topography with LMR over Andes
T42
3x3
9x9
Note Each element has an 8x8 grid
10
Some test experiments
  • Experiments without physics
  • Run both CAM/EUL and CAM/SEACM without physics
    (only DC) with H-S forcing, topography and real
    ICs
  • Run the cases for 10 days with uniform
    resolution, T42 for both models, with the ICs
    from NCAR documentation
  • These experiments should give an indication of
    the quality of SEAM predictions.

11
Sea Level Pressure (hpc)
Dynamical cores W/o topo.
Seam
T 0 days
EUL
T 5 days
T 10 days
12
Sea Level Pressure (hpc)
Dynamical cores with topo.
Seam
T 0 days
EUL
T 5 days
T 10 days
13
More test experiments
  • Experiments with physics
  • Run both CAM/EUL and CAM/SEACM with physics,
    topography and real ICs
  • Run the cases for 10 days with uniform
    resolution, T42 for both models, with the ICs
    from NCAR documentation
  • These experiments should give an indication of
    the quality of SEACM predictions.

14
Sea Level Pressure (hpc)
CAM/Swamp w/o topo.
Seam
T 0 days
EUL
T 5 days
T 10 days
15
Some computation and timing results
  • Results are with DC SEAM and H-S forcing
  • Computations with various truncations and of
    processors
  • Computations with various computers and of
    processors.

16
Dynamical Core/SEAM
  • Held-Suarez forcing
  • SEAM with uniform grid
  • Scaling results for various resolutions almost
    insensitive to processor number change.

HP Exemplar SPP2000
320km/L20 160km/L20 80km/L20
320km/L20 (dotted) 160km/L20 (solid) 80km/L20
(dashed)
17
Dynamical Core/SEAM
  • Parallel scaling on various computers
  • Log-log plot, flops vs processors.

Gflops
  • Triangles denote SEAM
  • Horizontal resolution-T181, (g)seaborg- T533
  • Aries DyCore
  • Other symbols for other models

of processors
18
Breakdown of the Polar Stratospheric Vortex
  • 16-day simulation with SEAM
  • Highest resolution case
  • Horizontal Resolution 36 km (T363)
  • Vertical Resolution 200 levels
  • Domain global
  • Supercomputer IBM SP RS/6000
  • Grid Points 88780800
  • Results from simulations with SEAM and other
    models for coarser resolutions are available.

19
Polar vortex calculation comparisons
Cost per day per level
Ger. Icos. model
Eulerian
Finite-vol
Semi-Lag.
SEAM
20
  • Polar vortex evolution
  • potential vorticity
  • medium resolution(70 km)
  • view from space
  • 16 days

21
  • Polar vortex evolution
  • potential vorticity
  • medium resolution (70 km)
  • view from space, exaggerated height
  • 16 days

22
  • Polar vortex evolution
  • potential vorticity
  • high resolution (36 km)
  • view from space,exaggerated height
  • 16 days

23
  • Interactions
  • NCAR
  • CCM4 staff
  • SCD staff
  • Scientists associated with the project
  • Computers
  • NERSC
  • Computers and Support staff
  • ORNL
  • Computers and Support staff
  • UMCP
  • Scientists and students associated with the
    project
  • Stretched-grid development group.
  • Staff
  • PIs Baer, Tribbia, Fournier
  • Postdoc Wang
  • Co-Investigator Taylor
  • Faculty Affiliate Fox-Rabinovitz
  • Collaborators Thomas, Loft

24
The End
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